Astrocyte Autophagy Flux Protects Neurons Against Oxygen-Glucose Deprivation and Ischemic/Reperfusion Injury

Jiawei Bai-Hu-Decoction ameliorated heat stroke-induced brain injury by inhibiting TLR4/NF-κB signal and mitophagy of glial cell

ETHNOPHARMACOLOGICAL RELEVANCE

Jiawei Bai-Hu-Decoction (JWBHD), a prescription formulated with seven traditional Chinese medicinal material has demonstrated clinical efficacy in mitigating brain injury among heat stroke (HS) patients.

AIM OF THE STUDY

This study aimed to evaluate the therapeutic efficacy of JWBHD on rat model of HS and to explore its therapeutic mechanisms by integrating network pharmacology and pharmacodynamic methodologies, which major components were analyzed by using UPLC-MS/MS.

MATERIALS AND METHODS

The network pharmacology analysis was firstly conducted to predict the potential active ingredients and therapeutic targets of JWBHD. The anti-HS effectiveness of JWBHD was then evaluated on rats experienced HS. Rat brain tissues were harvested for a comprehensive array of experiments, including western blot, PCR, H&E staining, Nissl staining, ELISA, transmission electron microscope, flow cytometry and immunofluorescence to validate the protective effects of JWBHD against HS-induced brain damage. Furthermore, the inhibitory effects of JWBHD on TLR4/NF-κB signal and mitophagy of glial were further verified on HS-challenged F98 cell line. Finally, the chemical compositions of the water extract of JWBHD were analyzed by using UPLC-MS/MS.

RESULTS

Network pharmacology has identified fifty core targets and numerous HS-related signaling pathways as potential therapeutic targets of JWBHD. Analysis of protein-protein interaction (PPI) and GO suggests that JWBHD may suppress HS-induced inflammatory signals. In experiments conducted on HS-rats, JWBHD significantly reduced the core temperature, restored blood pressure and alleviated neurological defect. Furthermore, JWBHD downregulated the counts of white blood cells and monocytes, decreased the levels of inflammatory cytokines such as IL-1β, IL-6 and TNF-α in peripheral blood, and suppressed the expression of TLR4 and NF-κB in the cerebral cortex of HS-rats. Besides, JWBHD inhibited the apoptosis of cortical cells and mitigated the damage to the cerebral cortex in HS group. Conversely, overactive mitophagy was observed in the cerebral cortex of HS-rats. However, JWBHD restored the mitochondrial membrane potential and downregulated expressions of mitophagic proteins including Pink1, Parkin, LC3B and Tom20. JWBHD reduced the co-localization of Pink1 and GFAP, a specific marker of astrocytes in the cerebral cortex of HS-rats. In addition, the inhibitory effect of JWBHD on TLR4/NF-κB signaling and overactive mitophagy were further confirmed in F98 cells. Finally, UPLC-MS/MS analysis showed that the main components of JWBHD include isoliquiritigenin, liquiritin, dipotassium glycyrrhizinate, ginsenoside Rb1, ginsenoside Re, etc. CONCLUSIONS: JWBHD protected rats from HS and prevented HS-induced damage in the cerebral cortex by suppressing TLR4/NF-κB signaling and mitophagy of glial.

Targeted Therapy of Spinal Cord Injury: Inhibition of Apoptosis Is a Promising Therapeutic Strategy

Spinal cord injury (SCI) is a serious disabling central nervous system injury that can lead to motor, sensory, and autonomic dysfunction below the injury level. SCI can be divided into primary injury and secondary injury according to pathological process. Primary injury is mostly irreversible, while secondary injury is a dynamic regulatory process. Apoptosis is an important pathological event of secondary injury and has a significant effect on the recovery of nerve function after SCI. Nerve cell death can further aggravate the microenvironment of the injured site, leading to neurological dysfunction and thus affect the clinical outcome of patients. Therefore, apoptosis plays a crucial role in the pathological progression of secondary SCI, while inhibiting apoptosis may be a promising therapeutic strategy for SCI. This review will summarize and explore the factors that lead to cell death after SCI, the influence of cross talk between signaling pathways and pathways involved in apoptosis and discuss the influence of apoptosis on SCI, and the therapeutic significance of targeting apoptosis on SCI. This review helps us to understand the role of apoptosis in secondary SCI and provides a theoretical basis for the treatment of SCI based on apoptosis.

Gene therapy of adeno-associated virus (AAV) vectors in preclinical models of ischemic stroke

Stroke has been associated with devastating clinical outcomes, with current treatment strategies proving largely ineffective. Therefore, there is a need to explore alternative treatment options for addressing post-stroke functional deficits. Gene therapy utilizing adeno-associated viruses (AAVs) as a critical gene vector delivering genes to the central nervous system (CNS) gene delivery has emerged as a promising approach for treating various CNS diseases. This review aims to provide an overview of the biological characteristics of AAV vectors and the therapeutic advancements observed in preclinical models of ischemic stroke. The study further investigates the potential of manipulating AAV vectors in preclinical applications, emphasizing the challenges and prospects in the selection of viral vectors, drug delivery strategies, immune reactions, and clinical translation.

Signaling pathways in brain ischemia: Mechanisms and therapeutic implications

Ischemic stroke occurs when the arteries supplying blood to the brain are narrowed or blocked, inducing damage to brain tissue due to a lack of blood supply. One effective way to reduce brain damage and alleviate symptoms is to reopen blocked blood vessels in a timely manner and reduce neuronal damage. To achieve this, researchers have focused on identifying key cellular signaling pathways that can be targeted with drugs. These pathways include oxidative/nitrosative stress, excitatory amino acids and their receptors, inflammatory signaling molecules, metabolic pathways, ion channels, and other molecular events involved in stroke pathology. However, evidence suggests that solely focusing on protecting neurons may not yield satisfactory clinical results. Instead, researchers should consider the multifactorial and complex mechanisms underlying stroke pathology, including the interactions between different components of the neurovascular unit. Such an approach is more representative of the actual pathological process observed in clinical settings. This review summarizes recent research on the multiple molecular mechanisms and drug targets in ischemic stroke, as well as recent advances in novel therapeutic strategies. Finally, we discuss the challenges and future prospects of new strategies based on the biological characteristics of stroke.

Curcumin protects from LPS-induced activation of astrocytes via AMPK pathway

Curcumin, a phenolic pigment, plays an inhibitory role in astrocytes activation which are involved in the pathogenesis of neurological diseases and inflammatory responses. The present study aimed to investigate the underlying regulatory mechanism behind the therapeutic effect of curcumin on the lipopolysaccharide (LPS)-activated astrocytes in vitro. Specifically, we investigated the inhibitory effect of curcumin on LPS-induced astrocyte's proliferation. Additionally, we investigated whether the adenosine-monophosphate-activated protein kinase signaling (AMPK) pathway was involved in this process. Our data demonstrated that curcumin significantly increased the level of phosphorylated AMPK protein in LPS-activated astrocytes. In addition, our data demonstrated that curcumin play an inhibitory role on the migration, autophagy, the pro-inflammatory mediators by the AMPK signaling pathway in LPS-activated astrocytes. These results could shed light on understanding of molecular mechanism for the inhibition of curcumin on migration, autophagy, and the pro-inflammatory mediators during the process of astrocyte activation, and might contribute to a promising therapeutic intervention in the neurological diseases-related astrocytes activation.

Astrocyte-Neuronal Communication and Its Role in Stroke

Astrocytes are the most abundant glial cells in the central nervous system. These cells are an important hub for intercellular communication. They participate in various pathophysiological processes, including synaptogenesis, metabolic transformation, scar production, and blood-brain barrier repair. The mechanisms and functional consequences of astrocyte-neuron signaling are more complex than previously thought. Stroke is a disease associated with neurons in which astrocytes also play an important role. Astrocytes respond to the alterations in the brain microenvironment after stroke, providing required substances to neurons. However, they can also have harmful effects. In this review, we have summarized the function of astrocytes, their association with neurons, and two paradigms of the inflammatory response, which suggest that targeting astrocytes may be an effective strategy for treating stroke.

AQP4 Aggravates Cognitive Impairment in Sepsis-Associated Encephalopathy through Inhibiting Nav 1.6-Mediated Astrocyte Autophagy

The pathology of sepsis-associated encephalopathy (SAE) is related to astrocyte-inflammation associated with aquaporin-4 (AQP4). The aim here is to investigate the effects of AQP4 associated with SAE and reveal its underlying mechanism causing cognitive impairment. The in vivo experimental results reveal that AQP4 in peripheral blood of patients with SAE is up-regulated, also the cortical and hippocampal tissue of cecal ligation and perforation (CLP) mouse brain has significant rise in AQP4. Furthermore, the data suggest that AQP4 deletion could attenuate learning and memory impairment, attributing to activation of astrocytic autophagy, inactivation of astrocyte and downregulate the expression of proinflammatory cytokines induced by CLP or lipopolysaccharide (LPS). Furthermore, the activation effect of AQP4 knockout on CLP or LPS-induced PPAR-γ inhibiting in astrocyte is related to intracellular Ca2+ level and sodium channel activity. Learning and memory impairment in SAE mouse model are attenuated by AQP4 knockout through activating autophagy, inhibiting neuroinflammation leading to neuroprotection via down-regulation of Nav 1.6 channels in the astrocytes. This results in the reduction of Ca2+ accumulation in the cell cytosol furthermore activating the inhibition of PPAR-γ signal transduction pathway in astrocytes.

GluA1 Degradation by Autophagy Contributes to Circadian Rhythm Effects on Cerebral Ischemia Injury

The mechanisms of many diseases, including central nervous system disorders, are regulated by circadian rhythms. The development of brain disorders such as depression, autism, and stroke is strongly associated with circadian cycles. Previous studies have shown that cerebral infarct volume is smaller at night (active phase) than during the day (inactive phase) in ischemic stroke rodent models. However, the underlying mechanisms remain unclear. Increasing evidence suggests that glutamate systems and autophagy play important roles in the pathogenesis of stroke. Here, we report that GluA1 expression was decreased and autophagic activity was increased in active-phase male mouse models of stroke compared with the inactive-phase models. In the active-phase model, induction of autophagy decreased the infarct volume, whereas inhibition of autophagy increased the infarct volume. Meanwhile, GluA1 expression was decreased following activation of autophagy and increased following inhibition of autophagy. We used Tat-GluA1 to uncouple p62, an autophagic adapter, from GluA1 and found that this blocked the degradation of GluA1, an effect similar to that of inhibition of autophagy in the active-phase model. We also demonstrated that knock-out of the circadian rhythm gene Per1 abolished the circadian rhythmicity of the volume of infarction and also abolished GluA1 expression and autophagic activity in wild-type (WT) mice. Our results suggest an underlying mechanism by which the circadian rhythm participates in the autophagy-dependent regulation of GluA1 expression, which influences the volume of infarction in stroke.SIGNIFICANCE STATEMENT Circadian rhythms affect the pathophysiological mechanisms of disease. Previous studies suggested that circadian rhythms affect the infarct volume in stroke, but the underlying mechanisms remain largely unknown. Here, we demonstrate that the smaller infarct volume after middle cerebral artery occlusion/reperfusion (MCAO/R) during the active phase is related to lower GluA1 expression and activation of autophagy. The decrease in GluA1 expression during the active phase is mediated by the p62-GluA1 interaction, followed by direct autophagic degradation. In short, GluA1 is the substrate of autophagic degradation, which mainly occurs after MCAO/R during the active phase but not the inactive phase.

Apelin-13 prevents the effects of oxygen-glucose deprivation/reperfusion on bEnd.3 cells by inhibiting AKT-mTOR signaling

Autophagy plays works by degrading misfolded proteins and dysfunctional organelles and maintains intracellular homeostasis. Apelin-13 has been investigated as an agent that might protect the blood-brain barrier (BBB) from cerebral ischemia/reperfusion (I/R) injury. In this study, we examined whether apelin-13 protects cerebral microvascular endothelial cells, important components of the BBB, from I/R injury by regulating autophagy. To mimic I/R injury, the mouse cerebral microvascular endothelia l cell line bEnd 3 undergoes the process of oxygen and glucose deprivation and re feeding in the process of culture. Cell viability was detected using a commercial kit, and cell migration was monitored by in vitro scratch assay. The tight junction (TJ) proteins ZO-1 and occludin; the autophagy markers LC3 II, beclin 1, and p62; and components of the AKT-mTOR signaling pathway were detected by Western blotting and immunofluorescence. To confirm the role of autophagy in OGD/R and the protective effect of apelin-13, we treated the cells with 3-methyladenine (3-MA), a pharmacological inhibitor of autophagy. Our results demonstrated that OGD/R increased autophagic activity but decreased viability, abundance of TJs, and migration. Viability and TJ abundance were further reduced when the OGD/R group was treated with 3-MA. These results indicated that bEnd.3 upregulates autophagy to ameliorate the effects of OGD/R injury on viability and TJs, but that the autophagy induced by OGD/R alone is not sufficient to protect against the effect on cell migration. Treatment of OGD/R samples with apelin-13 markedly increased viability, TJ abundance, and migration, as well as autophagic activity, whereas 3-MA inhibited this increase, suggesting that apelin-13 exerted its protective effects by upregulating autophagy.

Upregulation of glutamate transporter 1 by mTOR/Akt pathway in astrocyte culture during oxygen-glucose deprivation and reoxygenation

Astrocyte-specific glutamate transporter subtype 1 (GLT-1) plays an important role in influencing glutamate excitatory toxicity and preventing the death of excitatory toxic neurons. Although the mammalian target of rapamycin (mTOR)/protein kinase B(Akt)/nuclear factor kappa B signaling cascade is involved in the upregulation of astrocytic GLT-1 in oxygen-glucose deprivation (OGD), it is unclear whether the mTOR/Akt pathway is involved in astrocytic GLT-1 upregulation in OGD and reoxygenation (OGD/R). In this study, we found that the treatment of cultured astrocytes with rapamycin and triciribine led to the decreased astrocytes' protrusions, smaller nuclei, and an increased apoptotic rate. The inhibitors of mTOR complex 1 significantly increased the expression levels of phosphorylated Akt-Ser473 (p-Akt), phosphorylated Akt-Thr308(p-Akt), and GLT-1, while Akt-specific inhibitors blocked GLT-1 expression, suggesting that the mTOR/Akt pathway is involved in GLT-1 upregulation. We further demonstrated that astrocytes under OGD/R adapted to environmental changes through the mTOR/Akt pathway, mainly by altering cell morphology and apoptosis and upregulating the expression levels of p-Akt and GLT-1. Our results suggested that astrocytes may adapt to short-term ischemic-reperfusion injury by regulating cell morphology, apoptosis and GLT-1 upregulation.

The regulatory roles of circular RNAs via autophagy in ischemic stroke

Ischemic stroke (IS) is a severe disease with a high disability, recurrence, and mortality rates. Autophagy, a highly conserved process that degrades damaged or aging organelles and excess cellular components to maintain homeostasis, is activated during IS. It influences the blood–brain barrier integrity and regulates apoptosis. Circular RNAs (circRNAs) are novel non-coding RNAs involved in IS-induced autophagy and participate in various pathological processes following IS. In addition, they play a role in autophagy regulation. This review summarizes current evidence on the roles of autophagy and circRNA in IS and the potential mechanisms by which circRNAs regulate autophagy to influence IS injury. This review serves as a basis for the clinical application of circRNAs as novel biomarkers and therapeutic targets in the future.

Sodium Danshensu protects against oxygen glucose deprivation/reoxygenation-induced astrocytes injury through regulating NOD-like receptor pyrin domain containing 3 (NLRP3) inflammasome and tuberous sclerosis complex-2 (TSC2)/mammalian target of rapamycin (mTOR) pathways

BACKGROUND

Cerebral ischemic stroke is a serious condition with high incidence, mortality, and associated disability. Currently, effective therapeutic options are available for ischemic stroke are limited. Accumulating evidence indicates that sodium Danshensu, mono sodium compound derived from Salvia miltiorrhiza, plays protective roles in ischemic stroke. However, the underlying protective mechanism of sodium Danshensu in cerebral ischemic stroke remains unknown.

METHODS

In the current study, we explored the role and mechanism of sodium Danshensu on astrocytes exposed to oxygen-glucose deprivation/reoxygenation (OGD/R), which mimics the process of ischemia-reperfusion. The impact of sodium Danshensu on cell viability and apoptosis after OGD/R were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-dophenyl tetrazolium bromide (MTT) assay and flow cytometry. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and western blot were used to detect the expression of target messenger RNA (mRNA) and proteins associated with apoptosis and autophagy. The release of lactate dehydrogenase (LDH) was determined, and the production of proinflammatory cytokines were detected using enzyme-linked immunosorbent assay (ELISA) kits.

RESULTS

It was found that sodium Danshensu could significantly increase cell viability and decrease LDH release and apoptosis. Besides, it inhibited the production of proinflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6. Sodium Danshensu also dose-dependently decreased protein and mRNA levels of nucleotide binding oligomerization NOD-like receptor pyrin domain containing 3 (NLRP3) and high mobility group box 1 (HMGB1), which play a crucial role in promoting ischemic stroke-induced cell injury. Moreover, sodium Danshensu dose-dependently upregulated Beclin 1 expression, downregulated P62 protein expression, and further increased LC3B-II/LC3B-I ratio through inducing autophagy in astrocytes. Additionally, we noticed that sodium Danshensu dose-dependently increased tuberous sclerosis complex-2 (TSC2) protein expression, while significantly reduced the levels of mammalian target of rapamycin (mTOR) in the presence of OGD/R insult.

CONCLUSIONS

These findings suggest that sodium Danshensu protects against OGD/R-induced injury by modulating the NLRP3 inflammasome and TSC2/mTOR pathways.

New insights into the interplay between autophagy and oxidative and endoplasmic reticulum stress in neuronal cell death and survival

Autophagy is a dynamic process that maintains the normal homeostasis of cells by digesting and degrading aging proteins and damaged organelles. The effect of autophagy on neural tissue is still a matter of debate. Some authors suggest that autophagy has a protective effect on nerve cells, whereas others suggest that autophagy also induces the death of nerve cells and aggravates nerve injury. In mammals, oxidative stress, autophagy and endoplasmic reticulum stress (ERS) constitute important defense mechanisms to help cells adapt to and survive the stress conditions caused by physiological and pathological stimuli. Under many pathophysiological conditions, oxidative stress, autophagy and ERS are integrated and amplified in cells to promote the progress of diseases. Over the past few decades, oxidative stress, autophagy and ERS and their interactions have been a hot topic in biomedical research. In this review, we summarize recent advances in understanding the interactions between oxidative stress, autophagy and ERS in neuronal cell death and survival.

Lipid Microcapsules Promoted Neural Stem Cell Survival in the Infarcted Area of Mice with Ischemic Stroke by Inducing Autophagy

Intracerebral transplantation of neural stem cells (NSCs) for ischemic stroke treatment has been demonstrated to be inefficient, with only <5% of delivered cells being retained. Microcapsules may be a good carrier for NSC delivery; however, the current microcapsules do not fully meet the demands for cell survival after transplantation. In the present study, we designed a strategy for the encapsulation of NSCs in a novel lipid-alginate (L-A) microcapsule based on a two-step method. The protective effect of a L-A microcapsule on oxygen-glucose deprivation (OGD) was investigated by using the CCK8 test, the LDH release test, and flow cytometry. Mechanisms underlying the prosurvival effect were investigated by detecting autophagy markers like P62, LC3-I, and LC3-II, and autophagy flux analysis was also performed. Lastly, the ability of the L-A microcapsule to support NSCs delivery for ischemic stroke was investigated in the middle cerebral artery occlusion (MCAO) model. We found that L-A microcapsules exerted a good protective effect against OGD compared with control and alginate microcapsules. The L-A microcapsules were found to promote cell survival by not only providing a "physical" barrier but also altering autophagy markers like P62 and LC3-II, which enhanced autophagy flux. This novel microcapsule was confirmed to be suitable for NSC delivery in vivo, which alleviated transplanted NSC apoptosis, reduced the infarct volume, decreased brain edema, improved neurological deficit scores, and lastly, improved survival rate. The findings of this study may provide a new method for stem cell delivery, raising the prospect that intracerebral cell transplantation may be used to treat, for instance, ischemic stroke, traumatic brain injury, and so on.

Research progress on astrocyte autophagy in ischemic stroke

Ischemic stroke is a highly disabling and potentially fatal disease. After ischemic stroke, autophagy plays a key regulatory role as an intracellular catabolic pathway for misfolded proteins and damaged organelles. Mounting evidence indicates that astrocytes are strongly linked to the occurrence and development of cerebral ischemia. In recent years, great progress has been made in the investigation of astrocyte autophagy during ischemic stroke. This article summarizes the roles and potential mechanisms of astrocyte autophagy in ischemic stroke, briefly expounds on the crosstalk of astrocyte autophagy with pathological mechanisms and its potential protective effect on neurons, and reviews astrocytic autophagy-targeted therapeutic methods for cerebral ischemia. The broader aim of the report is to provide new perspectives and strategies for the treatment of cerebral ischemia and a reference for future research on cerebral ischemia.

The Emerging Role of Astrocytic Autophagy in Central Nervous System Disorders

Astrocytes act as "housekeeping cells" for maintaining cerebral homeostasis and play an important role in many disorders. Recent studies further highlight the contribution of autophagy to astrocytic functions, including astrogenesis, the astrocytic removal of neurotoxins or stressors, and astrocytic polarization. More importantly, genetic and pharmacological approaches have provided evidence that outlines the contributions of astrocytic autophagy to several brain disorders, including neurodegeneration, cerebral ischemia, and depression. In this study, we summarize the emerging role of autophagy in regulating astrocytic functions and discuss the contributions of astrocytic autophagy to different CNS disorders.

Mechanism of Ferroptosis and Its Role in Spinal Cord Injury

Ferroptosis is a non-necrotic form of regulated cell death (RCD) that is primarily characterized by iron-dependent membrane lipid peroxidation and is regulated by cysteine transport, glutathione synthesis, and glutathione peroxidase 4 function as well as other proteins including ferroptosis suppressor protein 1. It has been found that ferroptosis played an important role in many diseases, such as neurodegenerative diseases and ischemia-reperfusion injury. Spinal cord injury (SCI), especially traumatic SCI, is an urgent problem worldwide due to its high morbidity and mortality, as well as the destruction of functions of the human body. Various RCDs, including ferroptosis, are found in SCI. Different from necrosis, since RCD is a form of cell death regulated by various molecular mechanisms in cells, the study of the role played by RCD in SCI will contribute to a deeper understanding of the pathophysiological process, as well as the treatment and functional recovery. The present review mainly introduces the main mechanism of ferroptosis and its role in SCI, so as to provide a new idea for further exploration.

Novel Therapeutic Strategies for Ischemic Stroke: Recent Insights into Autophagy

Stroke is one of the leading causes of death and disability worldwide. Autophagy is a conserved cellular catabolic pathway that maintains cellular homeostasis by removal of damaged proteins and organelles, which is critical for the maintenance of energy and function homeostasis of cells. Accumulating evidence demonstrates that autophagy plays important roles in pathophysiological mechanisms under ischemic stroke. Previous investigations show that autophagy serves as a “double-edged sword” in ischemic stroke as it can either promote the survival of neuronal cells or induce cell death in special conditions. Following ischemic stroke, autophagy is activated or inhibited in several cell types in brain, including neurons, astrocytes, and microglia, as well as microvascular endothelial cells, which involves in inflammatory activation, modulation of microglial phenotypes, and blood-brain barrier permeability. However, the exact mechanisms of underlying the role of autophagy in ischemic stroke are not fully understood. This review focuses on the recent advances regarding potential molecular mechanisms of autophagy in different cell types. The focus is also on discussing the “double-edged sword” effect of autophagy in ischemic stroke and its possible underlying mechanisms. In addition, potential therapeutic strategies for ischemic stroke targeting autophagy are also reviewed.

Strategies for Biomaterial-Based Spinal Cord Injury Repair via the TLR4-NF-κB Signaling Pathway

The repair and motor functional recovery after spinal cord injury (SCI) has remained a clinical challenge. Injury-induced gliosis and inflammation lead to a physical barrier and an extremely inhibitory microenvironment, which in turn hinders the recovery of SCI. TLR4-NF-κB is a classic implant-related innate immunomodulation signaling pathway and part of numerous biomaterial-based treatment strategies for SCI. Numerous experimental studies have demonstrated that the regulation of TLR4-NF-κB signaling pathway plays an important role in the alleviation of inflammatory responses, the modulation of autophagy, apoptosis and ferroptosis, and the enhancement of anti-oxidative effect post-SCI. An increasing number of novel biomaterials have been fabricated as scaffolds and carriers, loaded with phytochemicals and drugs, to inhibit the progression of SCI through regulation of TLR4-NF-κB. This review summarizes the empirical strategies for the recovery after SCI through individual or composite biomaterials that mediate the TLR4-NF-κB signaling pathway.

Autophagy modulation in multiple sclerosis and experimental autoimmune encephalomyelitis

Multiple sclerosis (MS), a white matter demyelinating disease of the central nervous system (CNS), is characterized by neuroinflammatory and neurodegenerative. Experimental autoimmune encephalomyelitis (EAE) is a commonly used animal model for investigating pathogenic mechanisms of MS, representing the destruction of the blood-brain barrier (BBB), the activation of T cells, and the infiltration of myeloid cells. An increasing number of studies have documented that autophagy plays a critical role in the pathogenesis of both MS and EAE. Autophagy maintains CNS homeostasis by degrading the damaged organelles and abnormal proteins. Furthermore, autophagy is involved in inflammatory responses by regulating the activation of immune cells and the secretion of inflammatory factors. However, the specific mechanisms of autophagy involved in MS and EAE are not completely understood. In this review, we will summarize the complex mechanisms of autophagy in MS and EAE, providing potential therapeutic approaches for the management of MS.

Lentivirus- or AAV-mediated gene therapy interventions in ischemic stroke: A systematic review of preclinical in vivo studies

Due to the limited therapeutic options after ischemic stroke, gene therapy has emerged as a promising choice, especially with recent advances in viral vector delivery systems. Therefore, we aimed to provide the current state of the art of lentivirus (LV) and adeno-associated virus (AAV) mediated gene interventions in preclinical ischemic stroke models. A systematic analysis including qualitative and quantitative syntheses of studies published until December 2020 was performed. Most of the 87 selected publications used adult male rodents and the preferred stroke model was transient middle cerebral artery occlusion. LV and AAV vectors were equally used for transgene delivery, however loads of AAVs were higher than LVs. Serotypes having broad cell tropism, the use of constitutive promoters, and virus delivery before the stroke induction via stereotaxic injection in the cortex and striatum were preferred in the analyzed studies. The meta-analysis based on infarct volume as the primary outcome confirmed the efficacy of the preclinical interventions. The quality assessment exposed publication bias and setbacks in regard to risks of bias and study relevance. The translational potential could increase by using specific cell targeting, post-stroke interventions, non-invasive systematic delivery, and use of large animals.

Autophagy and Glycative Stress: A Bittersweet Relationship in Neurodegeneration

Autophagy is a fine-tuned proteolytic pathway that moves dysfunctional/aged cellular components into the lysosomal compartment for degradation. Over the last 3 decades, global research has provided evidence for the protective role of autophagy in different brain cell components. Autophagic capacities decline with age, which contributes to the accumulation of obsolete/damaged organelles and proteins and, ultimately, leads to cellular aging in brain tissues. It is thus well-accepted that autophagy plays an essential role in brain homeostasis, and malfunction of this catabolic system is associated with major neurodegenerative disorders. Autophagy function can be modulated by different types of stress, including glycative stress. Glycative stress is defined as a cellular status with abnormal and accelerated accumulation of advanced glycation end products (AGEs). It occurs in hyperglycemic states, both through the consumption of high-sugar diets or under metabolic conditions such as diabetes. In recent years, glycative stress has gained attention for its adverse impact on brain pathology. This is because glycative stress stimulates insoluble, proteinaceous aggregation that is linked to the malfunction of different neuropathological proteins. Despite the emergence of new literature suggesting that autophagy plays a major role in fighting glycation-derived damage by removing cytosolic AGEs, excessive glycative stress might also negatively impact autophagic function. In this mini-review, we provide insight on the status of present knowledge regarding the role of autophagy in brain physiology and pathophysiology, with an emphasis on the cytoprotective role of autophagic function to ameliorate the adverse effects of glycation-derived damage in neurons, glia, and neuron-glia interactions.

The Enantiomer of Allopregnanolone Prevents Pressure-Mediated Retinal Degeneration Via Autophagy

In an ex vivo rat ocular hypertension (OHT) model, the neurosteroid allopregnanolone (AlloP) exerts neuroprotective effects via enhancement of both GABA_A receptors and autophagy. We now examine whether its enantiomer (ent-AlloP), which is largely inactive at GABA receptors, offers similar neuroprotection in ex vivo and in vivo rat OHT models. Ex vivo rat retinal preparations were incubated in a hyperbaric condition (10 and 75 mmHg) for 24 h. An in vivo ocular hypertension (OHT) model was induced by intracameral injection of polystyrene microbeads. We examined pharmacological effects of AlloP, ent-AlloP, picrotoxin (a GABA_A receptor antagonist), and 3-MA (an autophagy inhibitor) histologically and biochemically. We found that both AlloP and ent-AlloP have marked neuroprotective effects in the retina, but effects of the unnatural enantiomer are independent of GABA_A receptors. Electron microscopic analyses show that pressure elevation significantly increased autophagosomes (APs) in the nerve fiber layer and addition of AlloP also increased APs and degenerative autophagic vacuoles (AVds). ent-AlloP markedly increased APs and AVds compared to AlloP. Examination of LC3B-II and SQSTM1 protein levels using immunoblotting revealed that AlloP increased LC3B-II, and ent-AlloP further enhanced LC3B-II and suppressed SQSTM1, indicating that autophagy is a major mechanism underlying neuroprotection by ent-AlloP. In an rat in vivo OHT model, single intravitreal ent-AlloP injection prevented apoptotic cell death of retinal ganglion cells similar to AlloP. However, even in this model, ent-AlloP was more effective in activating autophagy than AlloP. We conclude that ent-AlloP may be a prototype of potential therapeutic for treatment of glaucoma as an autophagy enhancer without affecting GABA receptors.

Deficiency in Androgen Receptor Aggravates Traumatic Brain Injury-Induced Pathophysiology and Motor Deficits in Mice

Androgens have been shown to have a beneficial effect on brain injury and lower reactive astrocyte expression after TBI. Androgen receptors (ARs) are known to mediate the neuroprotective effects of androgens. However, whether ARs play a crucial role in TBI remains unknown. In this study, we investigated the role of ARs in TBI pathophysiology, using AR knockout (ARKO) mice. We used the controlled cortical impact model to produce primary and mechanical brain injuries and assessed motor function and brain-lesion volume. In addition, the AR knockout effects on necrosis and autophagy were evaluated after TBI. AR knockout significantly increased TBI-induced expression of the necrosis marker alpha-II-spectrin breakdown product 150 and astrogliosis marker glial fibrillary acidic protein. In addition, the TBI-induced astrogliosis increase in ARKO mice lasted for three weeks after a TBI. The autophagy marker Beclin-1 was also enhanced in ARKO mice compared with wild-type mice after TBI. Our results also indicated that ARKO mice showed a more unsatisfactory performance than wild-type mice in a motor function test following TBI. Further, they were observed to have more severe lesions than wild-type mice after injury. These findings strongly suggest that ARs play a role in TBI.

Thrombin aggravates hypoxia/reoxygenation injury of astrocytes by activating the autophagy pathway mediated by SPRED2

Autophagy plays an important role in ischemia/reperfusion brain injury, however, the signaling pathways involved in cell autophagy are not fully understood. The present study aimed to investigate the roles and molecular mechanisms of thrombin and Sprouty-related EVH1 domain-2 (SPRED2) on autophagy in hypoxia/reoxygenation (H/R) induced astrocytes. Reverse transcription-quantitative PCR and western blot analyses were performed to detect the expression levels of thrombin and SPRED2. Western blot analysis was also performed to detect the protein expression levels of Beclin 1, microtubule-associated protein light chain 3 (LC3)-II and LC3-I. The MTT assay was performed to assess cell viability, while ELISA was performed to determine the supernatant levels of interleukin (IL)-1β, IL-6 and tumor necrosis factor-α. The results demonstrated that the effects of H/R induction on inflammatory factor secretion, oxidative stress, autophagy and cell viability in astrocytes were aggravated by thrombin, the effects of which were reversed following SPRED2 knockdown. Taken together, the results of the present study suggest that thrombin aggravates H/R injury in astrocytes by activating the SPRED2-mediated autophagy.

Impaired Mitophagy in Neurons and Glial Cells during Aging and Age-Related Disorders

Aging is associated with a decline in cognitive function, which can partly be explained by the accumulation of damage to the brain cells over time. Neurons and glia undergo morphological and ultrastructure changes during aging. Over the past several years, it has become evident that at the cellular level, various hallmarks of an aging brain are closely related to mitophagy. The importance of mitochondria quality and quantity control through mitophagy is highlighted by the contribution that defects in mitochondria-autophagy crosstalk make to aging and age-related diseases. In this review, we analyze some of the more recent findings regarding the study of brain aging and neurodegeneration in the context of mitophagy. We discuss the data on the dynamics of selective autophagy in neurons and glial cells during aging and in the course of neurodegeneration, focusing on three mechanisms of mitophagy: non-receptor-mediated mitophagy, receptor-mediated mitophagy, and transcellular mitophagy. We review the role of mitophagy in neuronal/glial homeostasis and in the molecular pathogenesis of neurodegenerative disorders, such as Parkinson's disease, Alzheimer's disease, and other disorders. Common mechanisms of aging and neurodegeneration that are related to different mitophagy pathways provide a number of promising targets for potential therapeutic agents.

GATA3 improves the protective effects of bone marrow-derived mesenchymal stem cells against ischemic stroke induced injury by regulating autophagy through CREG

BACKGROUND

Bone marrow-derived mesenchymal stem cells (BMSCs) transplantation has been demonstrated to benefit functional recovery after ischemic stroke, however, the low survival rate of BMSCs in ischemic microenvironment largely limits its use.

METHODS

Rat BMSCs (rBMSCs) were isolated from SD rats and treated with oxygen glucose deprivation/reoxygenation (OGD) to mimic ischemic microenvironment in vitro. Expression of mRNAs and proteins were assessed by qRT-PCR and western blot, respectively. Cell viability was detected using MTT. ROS level was evaluated by DCFH-DA Assay Kit. TUNEL and flow cytometry analysis were adopted to detect cell apoptosis. Immunofluorescence analysis was used to examine LC3 expression. Dual-luciferase reporter and ChIP assays were employed to determine the interaction between CREG and GATA3. Middle cerebral artery occlusion (MCAO) model was established to mimic ischemic stroke in vivo. TTC staining was used to measure the infarcts area in the brain of MCAO rats. Nissl staining was used to examine the quantity of neurons, and mNSS test was applied to compare behavioral functions of animals.

RESULTS

The rBMSCs were successfully isolated from SD rats. OGD exposure decreased the expression of GATA3 in rBMSCs, GATA3 overexpression alleviated OGD-induced cell injury and enhanced autophagy. Treatment with autophagy inhibitor (3-MA) abolished the protective effects of GATA3 against OGD-induced cell injury. GATA3 targeted the promoter of CREG and positively regulated its expression. The protective effect of GATA3 overexpression on autophagy during OGD exposure was reversed by CREG knockdown. Moreover, GATA3 overexpression improved the therapeutic effects of BMSCs transplantation on ischemic stroke in vivo.

CONCLUSION

Our results indicated that GATA3 overexpression improved the therapeutic effects of rBMSCs transplantation against ischemic stroke induced injury by regulating autophagy through CREG.

Commentary on Some Recent Theses Relevant to Combating Aging: April 2020

Theses reviewed in this issue include "Advanced Imaging Technologies for Combined Biomedical Ultrasound and Photoacoustic Imaging," "Engineering Bispecific Chimeric Antigen Receptors to Improve the Efficacy of Adoptive T-Cell Therapy," "Il-36 Gamma Promotes Anti-Tumor Immunity Through Therapeutic Induction of Tumor-Associated Tertiary Lymphoid Structures," "Investigating the Role of Matrix Vesicles During Aortic Valve Interstitial Cell Calcification," "Local Delivery of Cyclosporine and Erythropoietin Promotes Functional Recovery in a Rodent Model of Stroke Injury by Endogenous Tissue Repair," and "Targeting Primary Cilia-Mediated Mechanotransduction to Promote Whole Bone Formation."

ZNRF2 attenuates focal cerebral ischemia/reperfusion injury in rats by inhibiting mTORC1-mediated autophagy

Zinc and ring finger 2 (ZNRF2), an E3 ubiquitin ligase, plays a crucial role in many diseases. However, its role in cerebral ischemia/reperfusion injury (CIRI) still remains unknown. In this study, the function and molecular mechanism of ZNRF2 in CIRI in vivo and vitro was studied. ZNRF2 was found to be dramatically downregulated in CIRI. Overexpression of ZNRF2 could significantly reduce the neurological deficit, brain infarct volume and histopathological damage of cortex in middle cerebral artery occlusion/reperfusion. Concomitantly, overexpression of ZNRF2 increased the primary neuronal viability and decreased the neuronal apoptosis induced by oxygen-glucose deprivation and reoxygenation (OGD/R). Mechanistically, overexpression of ZNRF2 inhibited the over-induction of autophagy induced by OGD/R which was abolished by mTORC1 inhibitor rapamycin. It can be concluded that ZNRF2 plays a protective effect in CIRI and the underlying mechanism may be related to the inhibition of mTORC1-mediated autophagy.

The neurosteroid allopregnanolone protects retinal neurons by effects on autophagy and GABRs/GABAA receptors in rat glaucoma models

In an ex vivo rat glaucoma model using dissected retinas, the neurosteroid allopregnanolone (AlloP) protects retinal ganglion cells (RGCs) via GABR/GABAA receptors. To determine the involvement of macroautophagy/autophagy in neuroprotection by AlloP, we examined the effects of autophagy activators, rapamycin and torin 2, and autophagy inhibitors, bafilomycin A1 and SAR405, on retinal retinal morphology and expression of MAP1 LC3B/LC3B (microtubule-associated protein 1 light chain 3 beta) and SQSTM1 (sequestosome 1). Administration of rapamycin or torin 2 exerted partial histological neuroprotection, while combined administration of AlloP with bafilomycin A1 or SAR405 induced severe degeneration in a hyperbaric condition. Electron microscopic analyses showed that the addition of AlloP significantly increased autophagosomes and degenerative autophagic vacuoles in the retinal nerve fiber layer. Immunoblotting showed that the addition of AlloP or autophagic activators increased the lipidated form of LC3B (LC3B-II) and suppressed SQSTM1. Moreover, bafilomycin A1 increased LC3B-II and SQSTM1 protein levels in the presence of AlloP without changes in corresponding mRNAs compared to AlloP-treated retinas in a hyperbaric condition. These data indicate that AlloP likely induces a protective form of autophagy in this model. In an in vivo rat model of glaucoma, we also observed neuroprotective effects of AlloP. Injection of polystyrene microbeads into the anterior chamber increased intraocular pressure about 3-fold and induced RGC apoptosis. A single intravitreal injection of AlloP or autophagy activators prevented apoptosis and protected RGCs with autophagy activation. We conclude that AlloP may serve as a potential therapeutic agent for the treatment of glaucoma via diverse mechanisms.Abbreviations: 2HBCD: 2-Hydroxypropyl)-β-cyclodextrin; 3-MA: 3-methyladenine; AlloP: allopregnanolone; AP: autophagosome; AVd: degradative autophagic vacuoles; GCL: ganglion cell layer; INL: inner nuclear layer; IOP: intraocular pressure; IPL: inner plexiform layer; LC3B-I: cytosolic form of LC3B; LCB-II: lipidated form of LC3B; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; mPTP: mitochondrial permeability transition pore; NDS: neuronal damage score; NFL: nerve fiber layer; OH: ocular hypertension; ON: optic nerve; ONL: outer nuclear layer; OPL: outer plexiform layer; p-STR: scotopic threshold response; RGC: retinal ganglion cells; RT-PCR: real-time reverse transcription polymerase chain reaction; SQSTM1: sequestosome 1; TUNEL: TdT-mediated dUTP Nick End Labeling.

Programmed cell death in spinal cord injury pathogenesis and therapy

Spinal cord injury (SCI) always leads to functional deterioration due to a series of processes including cell death. In recent years, programmed cell death (PCD) is considered to be a critical process after SCI, and various forms of PCD were discovered in recent years, including apoptosis, necroptosis, autophagy, ferroptosis, pyroptosis and paraptosis. Unlike necrosis, PCD is known as an active cell death mediated by a cascade of gene expression events, and it is crucial for elimination unnecessary and damaged cells, as well as a defence mechanism. Therefore, it would be meaningful to characterize the roles of PCD to not only enhance our understanding of the pathophysiological processes, but also improve functional recovery after SCI. This review will summarize and explore the most recent advances on how apoptosis, necroptosis, autophagy, ferroptosis, pyroptosis and paraptosis are involved in SCI. This review can help us to understand the various functions of PCD in the pathological processes of SCI, and contribute to our novel understanding of SCI of unknown aetiology in the near future.

Autophagy in Multiple Sclerosis: Two Sides of the Same Coin

Multiple sclerosis (MS) is a complex auto-immune disorder of the central nervous system (CNS) that involves a range of CNS and immune cells. MS is characterized by chronic neuroinflammation, demyelination, and neuronal loss, but the molecular causes of this disease remain poorly understood. One cellular process that could provide insight into MS pathophysiology and also be a possible therapeutic avenue, is autophagy. Autophagy is an intracellular degradative pathway essential to maintain cellular homeostasis, particularly in neurons as defects in autophagy lead to neurodegeneration. One of the functions of autophagy is to maintain cellular homeostasis by eliminating defective or superfluous proteins, complexes, and organelles, preventing the accumulation of potentially cytotoxic damage. Importantly, there is also an intimate and intricate interplay between autophagy and multiple aspects of both innate and adaptive immunity. Thus, autophagy is implicated in two of the main hallmarks of MS, neurodegeneration, and inflammation, making it especially important to understand how this pathway contributes to MS manifestation and progression. This review summarizes the current knowledge about autophagy in MS, in particular how it contributes to our understanding of MS pathology and its potential as a novel therapeutic target.

miR‑187‑3p inhibitor attenuates cerebral ischemia/reperfusion injury by regulating Seipin‑mediated autophagic flux

MicroRNAs (miRNAs/miRs) have been reported to affect ischemia/reperfusion (I/R)-induced cerebral damage. miRNAs cause post-transcriptional gene silencing by binding to the protein-coding sequence (CDS) of mRNAs. Seipin has a potential role in regulating autophagic flux. The present study investigated the involvement of miR-187-3p in Seipin expression, autophagic flux and apoptosis in vitro, as well as the underlying mechanism, using PC12 cells exposed to oxygen-glucose deprivation/reoxygenation (OGD/R), which mimicked the process of I/R. In comparison with control PC12 cells, OGD/R caused an increase in the level of miR-187-3p and a decrease in Seipin protein levels without changes in the level of Seipin mRNA. Using bioinformatics analysis, it was identified that miR-187-3p could bind to the CDS of Seipin. miR-187-3p inhibitor attenuated the reduction in Seipin protein expression in OGD/R-treated PC12 cells. Following OGD/R, autophagic flux was reduced and apoptosis was enhanced, which were attenuated by inhibition of miR-187-3p. Compared with OGD/R-treated PC12 cells, Seipin knockdown further impaired autophagic flux and promoted neuronal apoptosis, which were insensitive to inhibition of miR-187-3p. Furthermore, treatment with miR-187-3p inhibitor could decrease the infarction volume in a rat model of middle cerebral artery occlusion/reperfusion. The present findings indicated that miR-187-3p inhibitor attenuated ischemia-induced cerebral damage by rescuing Seipin expression to improve autophagic flux.

Delta opioid peptide [d-Ala2, d-Leu5] enkephalin confers neuroprotection by activating delta opioid receptor-AMPK-autophagy axis against global ischemia

Background

Ischemic stroke poses a severe risk to human health worldwide, and currently, clinical therapies for the disease are limited. Delta opioid receptor (DOR)-mediated neuroprotective effects against ischemia have attracted increasing attention in recent years. Our previous studies revealed that DOR activation by [d-Ala2, d-Leu5] enkephalin (DADLE), a selective DOR agonist, can promote hippocampal neuronal survival on day 3 after ischemia. However, the specific molecular and cellular mechanisms underlying the DOR-induced improvements in ischemic neuronal survival remain unclear.

Results

We first detected the cytoprotective effects of DADLE in an oxygen–glucose deprivation/reperfusion (OGD/R) model and observed increased viability of OGD/R SH-SY5Y neuronal cells. We also evaluated changes in the DOR level following ischemia/reperfusion (I/R) injury and DADLE treatment and found that DADLE increased DOR levels after ischemia in vivo and vitro. The effects of DOR activation on postischemic autophagy were then investigated, and the results of the animal experiment showed that DOR activation by DADLE enhanced autophagy after ischemia, as indicated by elevated LC3 II/I levels and reduced P62 levels. Furthermore, the DOR-mediated protective effects on ischemic CA1 neurons were abolished by the autophagy inhibitor 3-methyladenine (3-MA). Moreover, the results of the cell experiments revealed that DOR activation not only augmented autophagy after OGD/R injury but also alleviated autophagic flux dysfunction. The molecular pathway underlying DOR-mediated autophagy under ischemic conditions was subsequently studied, and the in vivo and vitro data showed that DOR activation elevated autophagy postischemia by triggering the AMPK/mTOR/ULK1 signaling pathway, while the addition of the AMPK inhibitor compound C eliminated the protective effects of DOR against I/R injury.

Conclusion

DADLE-evoked DOR activation enhanced neuronal autophagy through activating the AMPK/mTOR/ULK1 signaling pathway to improve neuronal survival and exert neuroprotective effects against ischemia.

The Contribution of Astrocyte Autophagy to Systemic Metabolism

Autophagy is an essential mechanism to maintain cellular homeostasis. Besides its role in controlling the quality of cytoplasmic components, it participates in nutrient obtaining and lipid mobilization under stressful conditions. Furthermore, autophagy is involved in the regulation of systemic metabolism as its blockade in hypothalamic neurons can affect the central regulation of metabolism and impact body energy balance. Moreover, hypothalamic autophagy can be altered during obesity, one of the main alterations of metabolism nowadays. In this review, we focus on the role of astrocytes, essential cells for brain homeostasis, which represent key metabolic regulators. Astrocytes can sense metabolic signals in the hypothalamus and modulate systemic functions as glucose homeostasis and feeding response. Moreover, the response of astrocytes to obesity has been widely studied. Astrocytes are important mediators of brain inflammation and can be affected by increased levels of saturated fatty acids associated with obesity. Although autophagy plays important roles for astrocyte homeostasis and functioning, the contribution of astrocyte autophagy to systemic metabolism has not been analyzed yet. Furthermore, how obesity can impact astrocyte autophagy is poorly understood. More studies are needed in order to understand the contribution of astrocyte autophagy to metabolism.

Role of miR-326 in neonatal hypoxic-ischemic brain damage pathogenesis through targeting of the δ-opioid receptor

Hypoxic-ischemic brain damage (HIBD) is a relatively common malignant complication that occurs in newborn infants, but promising therapies remain limited. In this study, we focused on the role of miR-326 and its target gene δ-opioid receptor (DOR) in the pathogenesis of neonatal HIBD. The expression levels of miR-326 and DOR after hypoxic-ischemic injury were examined both in vivo and in vitro. The direct relationship between miR-326 and DOR was confirmed by a dual-luciferase reporter assay. Further, effects of miR-326 on cell viability and apoptosis levels under oxygen glucose deprivation (OGD) were analyzed. The expression levels of miR-326 were significantly lower and DOR levels were significantly higher in the HIBD group than the control group both in vivo and in vitro. Overexpression of miR-326 downregulated the expression of DOR, while suppression of miR-326 upregulated the expression of DOR. The dual-luciferase reporter assay further confirmed that DOR could be directly targeted and regulated by miR-326. MiR-326 knockdown improved cell survival and decreased cell apoptosis by decreasing the expression levels of Caspase-3 and Bax and increasing Bcl-2 expression in PC12 cells after exposure to OGD. Moreover, DOR knockdown rescued the effect of the improved cell survival and suppressed cell apoptosis induced by silencing miR-326. Our findings indicated that inhibition of miR-326 may improve cell survival and decrease cell apoptosis in neonatal HIBD through the target gene DOR.

Aspects of the immune system that impact brain function

The conditions required for effective immune responses to viral or bacterial organisms and chemicals of exogenous origin and to intrinsic molecules of abnormal configuration, are briefly outlined. This is followed by a discussion of endocrine and environmental factors that can lead to excessive continuation of immune activity and persistent elevation of inflammatory responses. Such disproportionate activity becomes increasingly pronounced with aging and some possible reasons for this are considered. The specific vulnerability of the nervous system to prolonged immune events is involved in several disorders frequently found in the aging brain. In addition of being a target for inflammation associated with neurodegenerative disease, the nervous system is also seriously impacted by systemically widespread immune disturbances since there are several means by which immune information can access the CNS. The activation of glial cells and cells of non-nervous origin that form the basis of immune responses within the brain, can occur in differing modes resulting in widely differing consequences. The events underlying the relatively frequent occurrence of derangement and hyperreactivity of the immune system are considered, and a few potential ways of addressing this common condition are described.

Treadmill exercise improves neurological function by inhibiting autophagy and the binding of HMGB1 to Beclin1 in MCAO juvenile rats

AIMS

Treadmill exercise is a beneficial treatment following childhood stroke. Thus, studies focusing on the neuroprotective mechanism of exercise training during postischemic treatment in children with ischemic stroke are urgently needed. We evaluated the effects of treadmill exercise on autophagy after cerebral ischemia in young rats.

MAIN METHODS

Rats (23-25 days old) underwent cerebral ischemia-reperfusion (CI/R) surgery. The experimental animals were divided into 5 groups, and some groups received either treadmill exercise, a rapamycin (RAPA) injection or combination therapy for 3 or 7 days. We performed a series of experimental tests including neurological scoring, hematoxylin-eosin staining (H&E), Nissl staining, triphenyl tetrazolium chloride (TTC) staining, Western blot analysis (WB), immunofluorescence (IF), enzyme-linked immunosorbent assay (ELISA), transmission electron microscopy (TEM) and Terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling (TUNEL) fluorescence.

KEY FINDINGS

The experimental data indicated that treadmill exercise inhibited autophagy in the ischemic penumbra, inhibited high mobility group box 1 (HMGB1) translocation and binding to Beclin1, reduced apoptosis, reduced infarct volumes, and aided in functional recovery. However, RAPA promoted the opposite effects of treadmill exercise.

SIGNIFICANCE

We found that treadmill exercise improves the neurological deficits induced by CI/R by inhibiting autophagy and HMGB1 binding to Beclin1.

Commentary on Some Recent Theses Relevant to Combating Aging: April 2019

Theses reviewed in this issue include "Alpha-Synuclein Oligomers: Cellular Mechanisms and Aspects of Antibody Treatment," "Cx3cr1/cx3cl1 Axis Drives the Migration and Maturation of Oligodendroglia in the Central Nervous System," "Genome-Wide Expression Profiling of Human Circulating Monocytes and Macrophages Identifies Diagnostic and Prognostic Signatures for Cancer Outcomes," "Lysosomal Oxidation of Low Density Lipoproteins," and "The Senescence-Associated Secretory Phenotype Induced by ID1-p16 Axis Contributes to Sorafenib Resistance in Hepatocellular Carcinoma."

Proteostasis During Cerebral Ischemia

Cerebral ischemia is a complex pathology involving a cascade of cellular mechanisms, which deregulate proteostasis and lead to neuronal death. Proteostasis refers to the equilibrium between protein synthesis, folding, transport, and protein degradation. Within the brain proteostasis plays key roles in learning and memory by controlling protein synthesis and degradation. Two important pathways are implicated in the regulation of proteostasis: the unfolded protein response (UPR) and macroautophagy (called hereafter autophagy). Both are necessary for cell survival, however, their over-activation in duration or intensity can lead to cell death. Moreover, UPR and autophagy can activate and potentiate each other to worsen the issue of cerebral ischemia. A better understanding of autophagy and ER stress will allow the development of therapeutic strategies for stroke, both at the acute phase and during recovery. This review summarizes the latest therapeutic advances implicating ER stress or autophagy in cerebral ischemia. We argue that the processes governing proteostasis should be considered together in stroke, rather than focusing either on ER stress or autophagy in isolation.

Commentary on Some Recent Theses Relevant to Combating Aging: June 2019

Theses reviewed in this issue include "Age-Associated Lamin-B1 Reduction in the Thymic Epithelial Cells and Its Role in Thymic Involution," "Brainstem Structural Integrity in the Progression of Alzheimer's Disease," "Challenging Current Paradigms: Increasing the Efficacy of Radiation Therapy with Novel Radiation Schemes," "Cross-Talk Between the Skeletal Muscle Stem Cells and Endothelial Cells," "Design and Synthesis of Enzyme-MOF (Metal-Organic Framework) Composites for Long-Persistent Biomedical Applications," and "Megakaryocyte-Membrane Wrapped Nanoparticles for Targeted Delivery to Hematopoietic Stem Cells."

The Relationship Between Autophagy and Brain Plasticity in Neurological Diseases

Autophagy, a catabolic degradation system, is utilized for destroying and recycling the damaged or unnecessary cellular components. Brain plasticity refers to the remarkable characteristics of brain neurons that change their structure and function according to previous experience. This review was performed by searching the relevant articles in databases of SCIENCEDIRECT, PUBMED, and Web of Science, from respective inception to January 2019. Here, we review the neuroprotective effect of autophagy in neurological diseases and the mechanism of autophagy in brain plasticity. Moreover, the mechanism of autophagy in the process of brain plasticity can provide the possibility for the development of new treatment methods in the future, thus benefiting patients with neurological diseases. In summary, autophagy and brain plasticity play important roles in neurological diseases.

Homer1a Attenuates Endoplasmic Reticulum Stress-Induced Mitochondrial Stress After Ischemic Reperfusion Injury by Inhibiting the PERK Pathway

Homer1a is the short form of a scaffold protein that plays a protective role in many forms of stress. However, the role of Homer1a in cerebral ischemia/reperfusion (I/R) injury and its potential mechanism is still unknown. In this study, we found that Homer1a was upregulated by oxygen and glucose deprivation (OGD) and that overexpression of Homer1a alleviated OGD-induced lactate dehydrogenase (LDH) release and cell death in cultured cortical neurons. After OGD treatment, the overexpression of Homer1a preserved mitochondrial function, as evidenced by less cytochrome c release, less reactive oxygen species (ROS) production, less ATP and mitochondrial membrane potential (MMP) loss, less caspase-9 activation, and inhibition of endoplasmic reticulum (ER) stress confirmed by the decreased expression of phosphate-PKR-like ER Kinase (p-PERK)/PERK and phosphate- inositol-requiring enzyme 1 (p-IRE1)/IRE1 and immunofluorescence (IF) staining. In addition, mitochondrial protection of Homer1a was blocked by the ER stress activator Tunicamycin (TM) with a re-escalated ROS level, increasing ATP and MMP loss. Furthermore, Homer1a overexpression-induced mitochondrial stress attenuation was significantly reversed by activating the PERK pathway with TM and p-IRE1 inhibitor 3,5-dibromosalicylaldehyde (DBSA), as evidenced by increased cytochrome c release, increased ATP loss and a higher ROS level. However, activating the IRE1 pathway with TM and p-PERK inhibitor GSK2656157 showed little change in cytochrome c release and exhibited a moderate upgrade of ATP loss and ROS production in neurons. In summary, these findings demonstrated that Homer1a protects against OGD-induced injury by preserving mitochondrial function through inhibiting the PERK pathway. Our finding may reveal a promising target of protecting neurons from cerebral I/R injury.

The Application and Analytical Pathway of Dexmedetomidine in Ischemia/Reperfusion Injury

Ischemia/reperfusion cerebral injury can cause serious damage to nerve cells. The injured organelles are cleared by autophagy eventually, which is critical for cell survival. Dexmedetomidine is neuroprotective in various ischemia/reperfusion models. Mitochondrial calcium uniporter (MCU) is the most important channel of mitochondrial Ca²⁺ influx into mitochondria, where Ca²⁺ has a potential effect on mitochondrial autophagy. However, the role of MCU in the changes of mitophagy and autophagy caused by dexmedetomidine is unknown. In this study, we constructed an in vitro I/R model by subjecting the oxygen and glucose deprivation/reperfusion model to SH-SY5Y cells to mimic the cerebral I/R injury. We found that postconditioning with dexmedetomidine and 3-methyladenine (3MA, an autophagy inhibitor) increased the cell survival meanwhile reduced the production of autophagic vesicles and the expression of LC3 and Beclin 1. This process also increased the expression of BCL-2, P62, and TOM20. After applied with spermine (MCU-specific agonist), the expression of autophagy proteins by dexmedetomidine was reversed, and the same changes were also observed in immunofluorescence. The results of our study suggested that dexmedetomidine can inhibit MCU and reduce excessive mitophagy and autophagy for conferring protection against I/R injury.

The cytological mechanism and effects of hypertensive cerebral hemorrhage treatment by citicoline on serum GFAP and copeptin level

In this study, 102 patients with hypertensive intracerebral hemorrhage (52 patients in the citicoline treatment group and 50 patients in the routine treatment group) were analyzed and compared. It was found that citicoline-assisted treatment of hypertensive intracerebral hemorrhage could inhibit the release of serum glial fibrillary acidic protein (GFAP) and peptides ( P < 0.05) and improve the prognosis and neurological and daily living ability of patients ( P < 0.05). In addition, CDP-choline reduced the mortality of neurons, inhibited inflammatory factors, and improved the prognosis of patients ( P < 0.05). A high dose of CDP-choline was also significantly effective in protecting neurons.

The role of autophagy in acute brain injury: A state of flux?

It is established that increased autophagy is readily detectable after various types of acute brain injury, including trauma, focal and global cerebral ischemia. What remains controversial, however, is whether this heightened detection of autophagy in brain represents a homeostatic or pathologic process, or an epiphenomenon. The ultimate role of autophagy after acute brain injury likely depends upon: 1) the degree of brain injury and the overall autophagic burden; 2) the capacity of individual cell types to ramp up autophagic flux; 3) the local redox state and signaling of parallel cell death pathways; 4) the capacity to eliminate damage associated molecular patterns and toxic proteins and metabolites both intra- and extracellularly; and 5) the timing of the pro- or anti-autophagic intervention. In this review, we attempt to reconcile conflicting studies that support both a beneficial and detrimental role for autophagy in models of acute brain injury.